Strength of Super-Structure UN-ECE R66 Rollover Approval of Coaches based on Thin-Walled Framework Structures

Around 30,000 bus or coach occupants are injured every year in the European Union (EU).The prime objective of this paper is to describe Cranfield Impact Centre’s (CIC’s) structural crashworthiness approach for coach rollover certification process as defined by the United Nations-Economic Commission for Europe (UN-ECE) Regulation R66 [1].CIC was instrumental in the formulation of UN-ECE Regulation R66, the first ever “virtual testing approach” approved by the UK Government, for coach rollover approval.The virtual testing approach is based on the concept of thin-walled framework structures through Finite Element (FE) modelling.It is supported by a series of static and dynamic tests of the floor, waist and roof cant-rail joints. The main reasons for component testing importance in determining the bus and coach super-structure collapse responses are twofold – Firstly, to provide a calculation model with elasto-plastic stiffness data for all the possible plastic hinge locations (recorded as moment/rotation data for each joint) and secondly, to assess the structural integrity of the super-structure joints under quasi-static and dynamic loadings.The R66 regulation has been adopted by EU member states, together with Australia, South Africa and India, in a modified form, to improve the occupant safety by providing a safe zone within the vehicle during rollover [1 and 3].The methodology adopted to develop the rollover coach models is based on extending the problem from a quasi-static approach to a more complex dynamic situation that includes the influence of super-structure to ground interactions.